Ethanol enhances expression of cell surface class I MHC antigens in a variety of cell lines. In an embryonic cell line, this increase is up to 10-fold. Ethanol treatment of L cells also induced increased cell surface expression of MHC antigens, with a concomitant increase in steady-state levels of RNA. This effect is promoter dependent and restricted, since not all gene products are elevated. The effective ethanol concentration (1%) is physiologically attainable. In a study of chronic alcoholics, it was found that the levels of Class I MHC antigens on their PBL was significantly higher than in normal controls.